Comment OP appears to have drank the Epic Games Kool-aid.
The world’s biggest video game, Fortnite, is only available on Epic Games Store for most platforms. Epic’s market share is gigantic, other video game developers just don’t benefit of it because Epic promotes their own stuff first and foremost. If Epic had a storefront monopoly, it would be classified as anti-competitive behaviour.
Better not tell anyone about DRM-free open source games on Steam then. Wouldn’t wanna burst anyone’s bubble.